STRIP BRUSHES are composed of a U-shaped metal profile (backing) in which the filament is lodged in a continuous row.

There are two types of metal backings: single band (side figure) and double band (details under). In the more traditional single band backing the filaments are fastened between the U-shaped band and a core wire.

In the double band backing the filaments are anchored between the external band (toothed) and the internal band.

The single band style is far more common. Double band backings are used for very heavy-duty applications.Strip brushes can be divided into three types:

SPIRAL - the brush is wound in a spiral shape and secured to a tube or shaft

LINEAR - the brush is straight and is cut to length during production

INTERCHANGEABLE SEGMENTS - the brush is composed of a roller fitted with interchangeable linear strip brushes

Because of their type of construction strip brushes are particularly suitable for making linear elements or medium/large size rollers.Moreover, strip brushes are less versatile and less precise than punched brushes.

BACKING DIMENSIONS

Backing width B is a fundamental parameter in designing a strip brush. This factor defines several other parameters including the fill density and the level of stress that the brush will be able to withstand.The cross section of the metal backings and a side view of a double strip backing are shown in the figure 2.3.The table 2.1 shows the relative dimensions in accordance with backing B.

SPIRAL PITCH

The spiral pitch P (see figure 2.4) is the most critical parameter affecting the density of the strip brush. However a very densely filled brush is not always required. For example, if the brush is needed to remove debris and discharge the material easily the pitch must be sufficiently large to prevent the material from building up between the coils and clogging the brush. The minimum value of P is the same as the backing value B. The maximum value of P depends on the winding diameter D2: the greater dimension D2 the larger the maximum pitch. The following limits can be established:

In addition to defining the brush fill density, the winding pitch can be exploited to perform a mechanical transport function. If P is sufficiently large to accommodate all or a portion of the parts to be handled, the brush will function as an auger and its rotation will result in transverse movement of the material.It is therefore important in this case to specify whether the spiral should be righthanded or left-handed. Finally, the roller can be equipped with two spiral strips (right and left) converging in the centre of the brush, so that the material is shifted to the centre or towards the two outer extremities.The brush-auger solution, which features very low noise operation, is particularly suitable for conveying very delicate materials.

LINEAR STRIP DIMENSIONS

Linear strip brushes features are shown in the table 2.1. Length L is unlimited because the brushes are made from a continuous strip. Total height H is restricted by the limit values shown in the table 2.2.

TAB 2.2

-

SINGLE BAND

DOUBLE BAND

B

4

5

6

8

10

13

14

17

20

6

8

Hmax

100

150

150

200

200

400

400

400

400

200

350

As for the spiral strip brushes, the limitations are mainly related to the diameter of winding D2 (Figure 2.4). In fact there is always a minimum value of D2 below which the strip can not be wrapped. These limits depend on the base B, and are reported in Table 2.3 (galvanized iron base). For steel bases you must increase the values of the Table 2.3 by 100%.Regarding the maximum diameter of the brush D1 (Figure 2.4), generally can not exceed the value D1=1000mm.